Foxes are territorial animals. If they ignore the scent marks/calls, a fight will take place that can sometimes result in the death of one or both.
Domination in family groups rarely results in bloodshed. The dominant fox approaches the subordinate, tail held high, ears erect, walking stiffly. The subordinate chooses to run, in which case they may be pursued for a short distance, or adopts a submissive posture, sometimes rolling on their back and screeching.
If two non-breeding vixens meet, both may feel superior but neither is confident. Lots of pushing and body slamming takes place and if this doesn’t settle differences they stand up on hind legs – forepaws on each other’s shoulders with mouths agape they scream at each other – the winner will be the one who manages to push the other off-balance and then chases them away.
In order to stop subordinate vixens mating, the dominant female will suppress them by generally pushing them around so that her litter has the best chance of survival (as no competition)
If there are multiple litters of cubs it could be down to the dominant vixen being killed and unable to prevent others from having cubs.
Foxes are territorial, with territory sizes being dependent on the amount of food available. A plentiful supply of food generally equates to a smaller territory, as the fox has to travel less far for food. Likewise, less food means a larger territory and fewer foxes per square area. This explains why people tend to see larger numbers in major cities, due to crammed houses/plenty of food available. Foxes may be less visible in rural areas where food is more sparse.